1. Field of the Invention
This invention relates to the field of data processing or data recording, and more specifically to data recording devices that transduce data relative to a recording media by operation of a flying head or transducer.
2. Description of the Related Art
As is well known in the data processing art, one form of data memory device comprises one or more moving recording surfaces upon which binary data is written, and/or from which binary data is read by the use of a data transducer or head that is constructed and arranged to fly over the recording surface with very close physical spacing thereto. An undesirable head crash occurs when the head physically engages the recording surface. Many well known types of head sliders have been originated to optimize the performance of such a flying head and to reduce the occurrence of a head crash.
As will be appreciated, state of the art flying heads generally tend to fly a greater distance above the recording surface when the surrounding air density is increased. Thus, for any given flying head memory device the tendency for the head to crash increases as the memory device is operated at lower air densities such as exists at higher and higher altitudes. In appreciation of this fact, manufacturers generally specify a maximum altitude at which operation of the flying head device is recommended.
While a head crash is generally undesirable in any type of rotating memory device, a particular problem exists in the type of rotating memory device that comprises one of more rigid magnetic recording disks having flying magneto-resistive (MR) heads associated therewith. With this type of device, a head crash generates heat that can be incorrectly interpreted as binary data read from the disk.
U.S. Pat. No. 5,233,482, incorporated herein by reference for the purpose of indicating the background of the present invention and illustrating the state of the art, discusses the thermal asperity problem that can occur when a flying magneto-resistive head mechanically collides with a protrusion on the surface of an adjacent disk. In this patent, detection of a thermal asperity causes a thermal asperity data detection mode of operation to be established. Thermal asperities are detected by sensing a shift in the baseline of the head's read signal.
The use of MR heads in magneto resistive disk memory products can cause a significant problem relative to meeting hard error data rate manufacturing specifications over an altitude range that is specified for the products. In particular, it has been found that media asperitis or high spots that fall just below the height at which the head flies shows no problem during manufacture at generally lower altitudes. However, when the products are later operated at high altitude, the head flies lower, and the head may now physically contact the media's asperity, causing a thermal asperity transient to occur in the head. This transient often causes an unrecoverable, or hard read, error to occur in the head's read signal.
While prior devices have to some extent dealt with the problem of head crashes, and with the problem of thermal asperity in MR head devices, the need remains in the art to provide an apparatus and method whereby testing or other operation of a flying head device will reliably operate to ensure future operation of the device at a known high altitude.